Chromium(VI) forms two different oxyanions, the orange dichromate ion, Cr 2 O 7 2− , and the yellow chromate ion, CrO 4 2− . (See the following photos.) The equilibrium reaction between the two ions is Cr 2 O 7 2 − ( a q ) + H 2 O ( l ) ⇌ 2 CrO 4 2 − ( a q ) + 2 H + ( a q ) Explain why orange dichromate solutions turn yellow when sodium hydroxide is added.
Chromium(VI) forms two different oxyanions, the orange dichromate ion, Cr 2 O 7 2− , and the yellow chromate ion, CrO 4 2− . (See the following photos.) The equilibrium reaction between the two ions is Cr 2 O 7 2 − ( a q ) + H 2 O ( l ) ⇌ 2 CrO 4 2 − ( a q ) + 2 H + ( a q ) Explain why orange dichromate solutions turn yellow when sodium hydroxide is added.
Solution Summary: The author explains the color and reaction between chromium (VI) oxyanions, and the reason of change in color of dichromate solution by adding sodium hydroxide.
In the video, we looked at the absorbance of a certain substance and how it varies
depending on what wavelength of light we are looking at. Below is a similar scan of a
different substance. What color BEST describes how this substance will appear?
Absorbance (AU)
Violet
Blue
Green
Orange
1.2
1.0-
0.8-
0.6-
0.4-
0.2
0.0
450
500
550
600
650
700
Wavelength (nm)
violet
indigo
blue
green
yellow orange
red
Red
O Cannot tell from this information
In the above graph, what causes -450 nm wavelength of light to have a higher
absorbance than light with a -550 nm wavelength? Check all that are true.
The distance the light travels is different
The different data points are for different substances
The concentration is different at different times in the experiment
Epsilon (molar absortivity) is different at different wavelengths
5. a. Data were collected for Trial 1 to determine the molar mass of a nonvolatile solid solute when dissolved in cyclo-
hexane. Complete the table for the analysis (See Report Sheet). Record calculated values with the correct number
of significant figures.
B. Freezing Point of Cyclohexane plus
Calculation Zone
Unknown Solute
2. Mass of cyclohexane (g)
10.14
Part C.4
3. Mass of added solute (g)
0.255
C. Calculations
1. k; for cyclohexane (°C⚫ kg/mol)
20.0
2. Freezing point change, AT, (°C)
3.04
Part C.6
3. Mass of cyclohexane in solution (kg)
4. Moles of solute, total (mol)
Show calculation.
5. Mass of solute in solution, total (g)
6. Molar mass of solute (g/mol)
Show calculation.
Chapter 12 Solutions
Bundle: Chemistry: An Atoms First Approach, 2nd, Loose-Leaf + OWLv2, 4 terms (24 months) Printed Access Card
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